1. Field of the Invention
The present invention relates to a method of producing nonionic surfactants low in alkylene oxides and low in 1,4-dioxane, by a catalytic method employing an alkali metal fatty alkoxide and to a method of producing said alkali metal fatty alkoxide.
2. Description of the Background
Because products containing nonionic surfactants are used essentially on a daily basis, and in view of the possible toxicological hazard of appreciable impurities of alkylene oxides and 1,4-dioxane in these surfactants, it is necessary to have a supply of surfactant products having very low levels of alkylene oxides and 1,4-dioxane.
The customary production of nonionic surfactants employs catalysis with Na ions and/or K ions. These ions are added to the likes of such reactants as alkylphenols, fatty alcohols, glycols, amines, fatty acids, and oils. Preferably, the Na and/or K ions are added in the form of NaOH, KOH, sodium methoxide, or potassium methoxide. Water of solution and water of reaction are removed under an inert nitrogen atmosphere. Then the reaction with the alkylene oxide is carried out.
According to U.S. Pat. No. 4,453,023, barium alkoxide can also be used as a catalyst. Barium alkoxide is produced, according to the U.S. patent, by reaction of barium metal with ethanol, followed by reaction with, e.g., ethylhexanol. Vacuum distillation is used to remove ethanol from the barium ethylhexanoxide which is produced.
Eur. Pat. 0 026 547 describes a similar catalyst preparation procedure, according to which alkoxides of Ca, Sr, or Ba may be prepared by reacting Ca, Sr, or Ba metal with ethanol, followed by reaction with decanol. The regenerated ethanol is then removed by applying a vacuum to the reaction mixture.
There are several disadvantages associated with the method of producing nonionic surfactants as disclosed in U.S. Pat. No. 4,453,023, and with the use of catalysts in the production of nonionic surfactants, which catalysts are prepared by the two-step method in which an alkali metal is reacted with ethanol, followed by reaction of the metal ethoxide with a higher alcohol. These disadvantages entail very high costs, as well as high residual contents of alkylene oxides (c. 200 ppm) and 1,4-dioxane (c. 5000 ppm). Further, there are problems associated with the use of metals for producing alkoxides, because of the liberation of water. Further, the products produced with ethylhexanoxide catalysts have a strong odor of ethylhexanol.
Thus, a need continues to exist for a method of manufacturing nonionic ethoxylated surfactants low in alkylene oxides and low in 1,4-dioxane.